Kobe Steel (Japan)

Nonlinear Model Predictive Control (NMPC) offers a powerful approach for controlling complex nonlinear systems, yet faces two key challenges. First, accurately modeling nonlinear dynamics remains difficult. Second, variables directly related to control objectives often cannot be directly measured during operation. Although high-cost sensors can measure these variables during model development, their use in practical deployment is typically infeasible. To overcome these limitations, we propose a Predictive Virtual Sensor Identification (PVSID) framework that leverages temporary high-cost sensors during the modeling phase to create virtual sensors for NMPC implementation. We validate PVSID on a Two-Degree-of-Freedom (2-DoF) direct-drive robotic arm with complex joint interactions. The tip position is measured using a motion capture system during modeling, while encoders and an Inertial Measurement Unit (IMU) are utilized in NMPC. Experimental results show that our NMPC with identified virtual sensors achieves precise tip trajectory tracking without requiring the motion capture system during operation. PVSID offers a practical solution for implementing optimal control in nonlinear systems where the measurement of key variables is constrained by cost or operational limitations.

This review is focused on FC-BENTEN, an advanced synchrotron X-ray experimental database developed at SPring-8 with support from Japan’s New Energy and Industrial Technology Development Organization (NEDO). Designed to advance polymer electrolyte fuel cells (PEFCs) research, FC-BENTEN addresses challenges in improving efficiency, durability, and cost-effectiveness through data-driven approaches informed by materials informatics (MI). Through standardization of protocols for sample preparation, data acquisition, analysis, and formatting, the database ensures high-quality, reproducible data essential for reliable scientific outcomes. FC-BENTEN streamlines metadata creation using automated processes and template-based tools, enhancing data management, accessibility, and interoperability. Security measures include two-factor authentication, safeguarding sensitive information and maintaining controlled user access. Planned integration with MI platforms will broaden data cross-referencing capabilities, facilitate PEFC applications expansion, and guide future research. This review discusses FC-BENTEN’s architectural framework, metadata standardization efforts, and role in advancing PEFC research through a high-throughput experimental workflow. It illustrates how data-driven methods and standardized practices contribute to innovation, underscoring databases’ potential to accelerate next-generation PEFC technologies development.

This study investigates the effects of alkali elements on metal transfer behavior in rutile flux-cored arc welding. Four types of prototype flux-cored wires with different sodium contents in the flux were fabricated. By using these wires, the influence mechanism of sodium on the metal transfer behavior was elucidated through shadowgraph measurements of the metal transfer behavior as well as spectroscopic and color image observations of the arc characteristics. It was found that the metal transfer between 190 A and 310 A was in the projected transfer mode and could be further classified into two sub-modes (type A and type B) based on the droplet formation process. A larger droplet was formed on the side of flux column in type A, while a smaller one was formed in the center covering the flux in type B. The metal transfer frequency became larger in the latter case for the same wire feeding speed. Type A tended to dominate in the lower current and lower sodium content conditions, while type B dominated in the opposite conditions. The dominant sub-mode was determined to depend on the Lorentz force acting on the droplet. At medium currents (250 A and 280 A), both sub-modes appeared in similar proportions. The maximum metal transfer frequency occurred at a particular sodium content. When the sodium content was smaller or larger, type A or type B became dominant, respectively. The sodium content at which the maximum frequency occurred decreased when the current increased. In type A, the iron plasma was widely distributed on the droplet side of the flux, while the sodium plasma was concentrated near the flux on the opposite side, so both were separated. In contrast, in type B, the sodium plasma was concentrated around the flux at the center and the iron plasma was widely distributed in the arc column, so both overlapped around the center. Sodium has a low boiling point and low ionization potential. In type A, the sodium vapor greatly increased the electrical conductivity of plasma around the flux column, so part of the current flowed from the wire through the sodium plasma to the weld pool. Accordingly, the current flowing through the bottom of the droplet to the arc decreased, leading to a lower arc pressure and recoil pressure under the droplet, and causing the metal transfer frequency to increase with sodium content. On the other hand, in type B, the sodium vaporization increased around the center, increasing the recoil pressure. In addition, the current density at the bottom of the droplet increased due to the current concentration in the arc, causing the arc pressure to rise. Therefore, the metal transfer frequency tended to decrease with sodium content. Due to the balance of these factors, the metal transfer frequency has a maximum at a particular sodium content.

Commonly, flow rate (ISO 4490, JIS Z 2502, MPIF Standard 3) is used to evaluate powder flow. However, it may not be possible to measure flow rate because powder is not discharged from the orifice, and sometimes flow rate does not correspond to the actual production of parts in terms of productibility or weight variation. To examine the evaluation method of powder flow for die filling, we conducted measurements using evaluation devices (die filling testing devices) which are close to the actual die filling of pressing machines, owned by three powder producing member companies of the Technical Committee for Metal Powders of the Japan Powder Metallurgy Association. In addition, the powders used for this evaluation were those used in actual production by three member companies who manufacture components, from the same committee. As a result, it was found that appropriate quantitative evaluation is possible within the range of standard parameter conditions. On the other hand, it was also found that valid evaluations could not be obtained outside this range. We would like to discuss the possibility of standardization by further limiting parameter conditions.

Flowability of powders is commonly evaluated using flow rate (ISO 4490, JIS Z2502, MPIF 3). However, in cases where the powder is not discharged from the Hall flowmeter, flow rate cannot be applied. Furthermore, the measured value of flow rate does not necessarily correspond to the flowability in the hopper or the fillability of die during the manufacturing process of sintered parts. The die filling test is a potential method for quantitatively evaluating the flowability of powders and is expected to be an alternative evaluation method to flow rate.

The declining quality of iron ore fines and increasing re-use requirement of steelmaking slag have led to higher Al2O3 content in sinter products. High grade concentrated hematite ore (concentrate) has been emerged as a potential solution for reducing Al2O3 levels of sinter. However, research regarding on the melting and assimilation behavior of concentrates in sintering process is limited. On the other hand, our previous work demonstrated that Parallel Granulation with Inclined Mixing of Limestone, based on the creation and mixing of pseudo-particles with high and low CaO/Fe2O3 ratios, can improve the sinter strength and productivity. To investigate the melting and assimilation characteristics of concentrates, we conducted melt dripping tests various kind of iron ore, revealing that adhesive layers with high concentrate content have low melt retention capacity. Furthermore, sinter pot tests under single granulation condition showed that when a large amount of concentrate is blended, fragile sinter cake is formed due to insufficient melting and assimilation. Sinter pot tests using Inclined Mixing of Limestone demonstrated that melting and assimilation are promoted by positioning concentrate near abundant melt sources.

<p>Weathering steel is a steel material to which appropriate amounts of elements effective in improving weathering performance have been added, forming a protective rust on the steel surface and inhibiting the progression of corrosion, which is expected to reduce maintenance costs such as repainting, as well as environmental impact. In Japan, weathering steel bridges began to be used in the late 1960s and have been useful in reducing LCC and environmental impact. To ensure the long‐ term durability of weathering steel bridges, it is necessary to avoid environments such as high salinity and wet environments, and Japanese steel‐making companies have developed technology to predict the amount of long‐term corrosion loss that takes into account the surrounding environment. This paper looks back on the application of weathering steel to bridges in Japan and introduces technology for evaluating its durability in the short term.</p>

The effects of stress, plastic strain, and hydrogen on hydrogen embrittlement fracture of hole-expanded transformation-induced plasticity-aided martensitic steel were investigated. The hydrogen embrittlement properties were evaluated by means of cathodic hydrogen charging to the hole-expanded specimen. The residual stress and plastic strain distributions in the hole-expanded specimens were analyzed using finite element analysis. The hydrogen content was measured using a thermal desorption spectrometer. Hydrogen embrittlement cracking occurred approximately 3 mm from the hole edge in the radial direction. As the crack propagated, it diverged in the circumferential direction. The fracture morphology primarily consisted of a mixture of intergranular and quasi-cleavage fractures. The tensile stress in the circumferential direction at the position where the hydrogen embrittlement crack was initiated was the highest, and the tensile stress in the radial direction and hydrostatic stress were also high. The hydrogen content in the vicinity of the hole edge of the hole-expanded specimen was the highest owing to the large amount of plastic strain applied by hole punching and hole expanding whereas the hydrogen content at the positions where the hydrogen embrittlement crack was propagated was not very high. Thus, the highest tensile stress in the circumferential direction is the controlling factor in the location of the crack initiation site and the direction of the initial crack and its growth during the initial phase. The high hydrostatic stress that causes hydrogen accumulation could also assist the crack initiation.